1. Field of the Invention
The present invention relates to a circuit arrangement for the coarse synchronization of carrier signals and pulse signals with data signals in a data receiver which receives data signals modulated by a data transmitter, and more particularly to an arrangement wherein the data receiver contains a carrier regulation stage generating the carrier signals, a pulse regulation stage generating the pulse signals, a demodulator demodulating the modulated data signals, by the carrier signals, and a sampler for sampling the demodulated data signals, using the pulse signals.
2. Description of the Prior Art
In a high-speed transmission of data by way of band-limited channels, single-sideband signals are often used. Transmission is effected, for example, with 64 kBit/s, by way of primary group connections, using amplitude modulation with partial response pulses of the class IV. The use of partial response pulses for the transmitting of data is already generally known in the art and has, for example, already been described in the publication of E. R. Kretzmer titled "Generalization of a Technique for Binary Data Communication", published in the IEEE Transactions on Communication Technology, COM-14 (1966), pp. 67 and 68. The partial response pulses are frequently designated as partial information pulses.
In the transmission of data in the primary group band of the carrier frequency long-distance traffic network, data are transmitted using amplitude modulation. In a data transmitter, partial response pulses are assigned to data emitted by a data source. Subsequently, there follows an amplitude modulation of the partial response pulses with the aid of carrier signals. The modulated data signals are transmitted to a data receiver which recovers the transmitted data. The data receiver contains a demodulator which demodulates the modulated data with the aid of further carrier signals. The demodulated data signal is sample at prescribed points in time with the aid of pulse signals. In a decoder the transmitted data are recovered from the sample data signals, and are fed to a data output.
In a carrier regulation stage or, respectively, a pulse regulation stage, the carrier signals and the pulse signals are continuously synchronized with the transmitted data signals. The capture range of these regulation stages is generally not large, however, so that an in-synchronization condition is not guaranteed at the beginning of a data transmission. For the in-synchronization condition of the carrier signals and of the pulse signals, it is already known to first transmit single pulses from the data transmitter to the data receiver. The intervals of the individual pulses are so great that they do not mutually influence one another. From the form of the pulses it is possible to derive regulation criteria with which an in-synchronization condition is made possible even with arbitrary beginning values of the carrier phase and of the pulse phase.
In the known coarse synchronization, not only must the transmission of data from the transmitter to the receiver be interrupted in one direction, but also in the opposite direction, since information must go to the transmitter from the receiver that a coarse synchronization is necessary. The two transmission directions are therefore no longer independent of each other in this case.